Uveitis with its related intraocular inflammation are major causes of legal blindness in the United States, and they are characterized essentially by inflammatory cell infiltration in the uvea. In these intraocular inflammations, the loss of vision is due to retinal and uveal tissue damage that is such primarily mediated by phagocytes. On activation the phagocytes release superoxide and various chemical mediators. The superoxide and its products cause peroxidation of retinal cell membranes leading to retinal degeneration. During the past award period, we showed that RPE generates a 75 kDa novel protein that down-regulates polymorphonuclear leukocytes and macrophages in release of superoxide. We called this protein "retinal pigment epithelial protective protein" (RPP). Based on the previous results, we propose the hypothesis that "RPP prevents the full expression of respiratory burst in inflammatory phagocytes." A corollary of this hypothesis is that the 75 kDa RPE protein (RPP) should protect the retina from damage in uveitis. We now propose to test the hypothesis and conduct in-depth studies on the protein in the following five specific aims: 1.Determine the mechanism by which RPP inhibits superoxide generation in activated phagocytes. 2.Determine the kinetics of RPP biosynthesis and processing, and the intracellular signaling pathways involved in release of RPP in response to selected pro-inflammatory cytokines. 3.Detect effects of RPP on phagocyte activation and release of pro- inflammatory mediators. 4.Determine the in-vivo protective effect of RPP in animals with experimental uveitis. 5.Clone the gene encoding the RPP. To assure successful completion of the specific aims, we have assembled multidisciplinry team of experts to undertake the studies. An in-depth study of RPP and proposed experiments to test the hypothesis should provide insight into the interaction of inflammatory cells with RPE, the role of RPE in the protection of the retina and choriocapillaris in uveitis and other pathologic processes, such as retinal or macular degeneration, that are mediated by activated macrophages. Furthermore, the studies on RPP should lead to the development of a novel therapeutic strategy for prevention of retinal degeneration in chronic uveitis.